A theoretical definition is a proposed way of thinking about potentially related events [1][2] Indeed, theoretical definitions contain built-in theories; they cannot be simply reduced to describing a set of observations. The definition may contain implicit inductions and deductive consequences that are part of the theory.[3] A theoretical definition of a term can change, overtime, based on the methods in the field that created it.

The term scientific theory is reserved for concepts that are widely acepted. A scientific law often refers to regularities that can be expressed by a mathematical statement. However, there is no consensus about the distinction between these terms.[4] Every scientific concept must have an operational definition, however the operational definition can use both direct observations and latent variables.[5]

The first postulate of special relativity theory that the speed of light in vacuum is the same to all inertial observers (i.e. it is a constant, and therefore a good measure of length). Of interest, this theoretical concept is the basis of an operational definition for the length of a metre is "the distance traveled by light in a vacuum during a time interval of 1/299,792,458 of a second". Thus we have defined 'metre' according to other ideas contained in modern scientific theory. Rejection of the theory underlying a theoretical definition leaves the definition invalid for use in argument with those who reject it — neither side will advance its position by using terms the others do not accept[citation needed].

Heat explains a collection of various laws of nature and that predict certain results.[2]

In psychology, the concept of intelligence is meant to explain corrolations in performance on certain cognitive tasks.[8] Recent models suggest several cognitive processes may be involved in tasks that have been associated with intelligence.[9] However, overall the "g" or general intelligence factor is relatively supported by research[10]